Fenix 3 uncontrolled reboots

Hi, I have the same problem, may I have some help? 

Hi, I've got the instruction form Garmin support and it helped with my problem. 

Here is what you can try. 

There may be corrupt data saved on your device causing it to malfunction. I recommend deleting certain folders from your unit via the computer in order to ensure any possible corruption is removed. Folders that can be safely cleared: (Note that your device may not have all of these folders) This will remove activities, courses and segments off of the device and when rebooting rebuild the folders with no data.

• Activities
• Courses
• Monitor
• Newfiles
• RemoteSW
• Summary
• Segments
• Workouts
• .tmp or .bak files

Use CAUTION when deleting. Do NOT delete unknown files; deleting wrong files from your mass storage device can cause adverse performance affects.

PC:

1. Connect the Garmin device to the computer
2. Go to your device using File Explore and This PC
3. Double-Click on the Garmin drive
4. Open the Garmin folder
5. Select all folders listed above
6. Press the Delete key on the keyboard
7. If prompted, click Yes to confirm the deletion
8. Click the Back button to return to the drive list
9. Right-click on Garmin drive
10. Click Eject
11. Unplug device from computer

Mac:

1. Connect the Garmin device to the computer
2. Open Finder
3. Click Go in the menu bar at the top of the screen
4. Click Computer
5. Double-click Garmin drive
6. Open the Garmin folder
7. Select all folders listed above
8. Drag the selected files to the trash
9. Click the Back button to return to the drive list
10. Right-click the Trash on the Dock
11. Click Empty Trash
12. Click Empty Trash to confirm
13. Right-click the Garmin drive
14. Click Eject “Garmin”
15. Unplug device from computer

Thank you! I'll give it a try!